A technique to culture rabbit uterine epithelial cells in chemically defined medium has been developed. Estrogens were found to increase cell proliferation, while progesterone antogonized this effect. The primary cultures were found to be made up of quiescent or nondividing and dividing cells which show interactions. The cultures were also found to produce the rabbit uterus secretory protein uteroglobin. We have found prostaglandin F2Alpha and uteroglobin to be growth factors for our cultured cells. Preliminary evidence suggests that uteroglobin acts by increasing the amount of specific binding of prostglandin F2Alpha by the cells. The aims of this proposal are to eludidate the effects and mechanism of action of uteroglobin on rabbit endometriu. We will characterize further the prostaglandin F2Alpha receptor through kinetic studies, competition binding determinations and Scatchard analysis using cell membrane preparations obtained from endometrium scraped from rabbit uteri or cultures of rabbit endometrium epithelial cells. We will then examine the effect(s) of uteroglobin upon those parameters and the characteristics of prostaglandin binding in membranes isolated from endometrium from rabbits at different times after hCG injection, modulating in this way the uteroglobin concentration in uterine fluid. We will later determine the mechanism of uteroglobin interaction with rabbit endometrium through binding (after 125 Iodination), biochemical and cell proliferation studies, using cultured cells and whole animals. In summary, we believe that a uteroglobin-prostaglandin system plays an important role in endometrium biology, and maybe in other tissues. It is expected that our studies will help to increase the knowledge in the area of Reproductive Biology and Pathology, and by providing information on how hormones and local factors regulate proliferation and differentiation of endometrium, which are mechanisms implicated in implantation and decidualization.